Anisotropic Guest Diffusion in the delta Crystalline Host phase of Syndiotactic Polystyrene: Transport Kinetics in Films with Three Different Uniplanar Orientations of the Host Phase

The sorption and desorption of a guest (1,2-dichloroethane) in syndiotactic polystyrene (s-PS) films, presenting three different kinds of uniplanar orientation ((010), (.hivin.210), or (002)) of the nanoporous host d phase, were studied, mainly by Fourier transform IR measurements. For guest uptake from dil. aq. solns. (e.g., 50 ppm), the sorption in the amorphous phase is negligible with respect to sorption in the nanoporous cryst. phase. Correspondingly the guest sorption and desorption kinetics are influenced by the orientation of the anisotropic host cryst. phase. In particular, as for the guest diffusivity (D) measured by both sorption and desorption expts., D(010) £ D(002) < D(unoriented) < D(.hivin.210). These results can be rationalized on the basis of previous mol. dynamics simulations, predicting an anisotropic guest diffusion in the d cryst. phase